The present invention generally relates to an electrochemical cell and, more particularly, to an electrochemical cell and method of assembling a cell having increased anode-to-cathode interface area.
Electrochemical cells are commonly employed to supply voltage for electrically operated devices, particularly for portable electrically operated devices. Currently, a number of popular alkaline cells of the generally cylindrical shape are commercially available in industry-recognized, standard sizes, including D-, C-, AA-, AAA-, and AAAA-size cells, as well as other sizes and configurations. Alkaline cells such as the aforementioned type commonly provide a predetermined open circuit voltage supply with limited service performance.
Conventional cylindrical alkaline cells generally have a cylindrically shaped steel can provided with a positive cover at one end and a negative cover at the opposite end. The cylindrical cell has a positive electrode, commonly referred to as the cathode, which is often formed of a mixture of manganese dioxide, graphite, potassium hydroxide solution, deionized water, and TEFLON.RTM. solution formed about the interior side surface of the cylindrical steel can. Typically, a cup-shaped separator is centrally disposed within an inner cylindrical volume of the can about the interior surface of the cathode. A negative electrode, commonly referred to as the anode, is typically formed of zinc powder, a gelling agent, and other additives, and is disposed with an electrolyte solution within the separator. One example of a conventional cylindrical cell is disclosed in U.S. Pat. No. 5,501,924, which is hereby incorporated by reference.
Conventional cells of the cylindrical type typically have a single anode and a single cathode assembled within the steel can with the separator interfaced therebetween. The cathode is typically disposed against the interior surface of the can, generally within an outer peripheral portion of the can, with a cylindrical cavity centrally formed in the cathode. A cup-shaped separator configured to an approximate size and shape of the cavity within the cathode is then inserted in the cavity. The separator generally has an anode-to-cathode interface generally defined by the shape and size of the anode and cathode, which is approximately equal to the surface area of the outer periphery of the cylindrical anode. In addition, the anode is generally shaped as a cylinder with a uniformly curved outer surface parallel to the container wall such that the cathode is not easily susceptible to breakage which can lead to ionic and electric discontinuity in the cell.
A primary goal in designing alkaline cells is to increase the service performance, which is the length of time for the cell to discharge under a given load to a specific voltage at which the cell is no longer useful for its intended purpose. Commercially available alkaline cells commonly have an external size that is defined by industry standards, thereby limiting the ability to increase the amount of active materials within the cell. Yet, the need to find new ways to increase service performance remains the goal of the cell designers.